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package org.apache.lucene.store;
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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import java.io.IOException;
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import java.util.HashMap;
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* Abstract base class for performing read operations of Lucene's low-level
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public abstract class DataInput implements Cloneable {
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private boolean preUTF8Strings; // true if we are reading old (modified UTF8) string format
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/** Call this if readString should read characters stored
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* in the old modified UTF8 format (length in java chars
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* and java's modified UTF8 encoding). This is used for
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* indices written pre-2.4 See LUCENE-510 for details. */
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public void setModifiedUTF8StringsMode() {
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preUTF8Strings = true;
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/** Reads and returns a single byte.
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* @see DataOutput#writeByte(byte)
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public abstract byte readByte() throws IOException;
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/** Reads a specified number of bytes into an array at the specified offset.
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* @param b the array to read bytes into
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* @param offset the offset in the array to start storing bytes
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* @param len the number of bytes to read
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* @see DataOutput#writeBytes(byte[],int)
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public abstract void readBytes(byte[] b, int offset, int len)
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/** Reads a specified number of bytes into an array at the
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* specified offset with control over whether the read
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* should be buffered (callers who have their own buffer
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* should pass in "false" for useBuffer). Currently only
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* {@link BufferedIndexInput} respects this parameter.
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* @param b the array to read bytes into
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* @param offset the offset in the array to start storing bytes
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* @param len the number of bytes to read
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* @param useBuffer set to false if the caller will handle
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* @see DataOutput#writeBytes(byte[],int)
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public void readBytes(byte[] b, int offset, int len, boolean useBuffer)
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// Default to ignoring useBuffer entirely
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readBytes(b, offset, len);
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/** Reads two bytes and returns a short.
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* @see DataOutput#writeByte(byte)
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public short readShort() throws IOException {
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return (short) (((readByte() & 0xFF) << 8) | (readByte() & 0xFF));
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/** Reads four bytes and returns an int.
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* @see DataOutput#writeInt(int)
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public int readInt() throws IOException {
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return ((readByte() & 0xFF) << 24) | ((readByte() & 0xFF) << 16)
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| ((readByte() & 0xFF) << 8) | (readByte() & 0xFF);
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/** Reads an int stored in variable-length format. Reads between one and
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* five bytes. Smaller values take fewer bytes. Negative numbers are not
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* @see DataOutput#writeVInt(int)
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public int readVInt() throws IOException {
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/* This is the original code of this method,
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* but a Hotspot bug (see LUCENE-2975) corrupts the for-loop if
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* readByte() is inlined. So the loop was unwinded!
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for (int shift = 7; (b & 0x80) != 0; shift += 7) {
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i |= (b & 0x7F) << shift;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7F) << 7;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7F) << 14;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7F) << 21;
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if ((b & 0x80) == 0) return i;
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assert (b & 0x80) == 0;
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return i | ((b & 0x7F) << 28);
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/** Reads eight bytes and returns a long.
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* @see DataOutput#writeLong(long)
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public long readLong() throws IOException {
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return (((long)readInt()) << 32) | (readInt() & 0xFFFFFFFFL);
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/** Reads a long stored in variable-length format. Reads between one and
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* nine bytes. Smaller values take fewer bytes. Negative numbers are not
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public long readVLong() throws IOException {
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/* This is the original code of this method,
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* but a Hotspot bug (see LUCENE-2975) corrupts the for-loop if
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* readByte() is inlined. So the loop was unwinded!
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for (int shift = 7; (b & 0x80) != 0; shift += 7) {
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i |= (b & 0x7FL) << shift;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 7;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 14;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 21;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 28;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 35;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 42;
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if ((b & 0x80) == 0) return i;
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i |= (b & 0x7FL) << 49;
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if ((b & 0x80) == 0) return i;
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assert (b & 0x80) == 0;
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return i | ((b & 0x7FL) << 56);
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* @see DataOutput#writeString(String)
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public String readString() throws IOException {
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return readModifiedUTF8String();
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int length = readVInt();
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final byte[] bytes = new byte[length];
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readBytes(bytes, 0, length);
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return new String(bytes, 0, length, "UTF-8");
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private String readModifiedUTF8String() throws IOException {
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int length = readVInt();
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final char[] chars = new char[length];
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readChars(chars, 0, length);
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return new String(chars, 0, length);
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/** Reads Lucene's old "modified UTF-8" encoded
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* characters into an array.
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* @param buffer the array to read characters into
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* @param start the offset in the array to start storing characters
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* @param length the number of characters to read
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* @see DataOutput#writeChars(String,int,int)
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* @deprecated -- please use readString or readBytes
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* instead, and construct the string
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* from those utf8 bytes
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public void readChars(char[] buffer, int start, int length)
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final int end = start + length;
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for (int i = start; i < end; i++) {
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buffer[i] = (char)(b & 0x7F);
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else if ((b & 0xE0) != 0xE0) {
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buffer[i] = (char)(((b & 0x1F) << 6)
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| (readByte() & 0x3F));
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buffer[i] = (char)(((b & 0x0F) << 12)
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| ((readByte() & 0x3F) << 6)
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| (readByte() & 0x3F));
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/** Returns a clone of this stream.
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* <p>Clones of a stream access the same data, and are positioned at the same
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* point as the stream they were cloned from.
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* <p>Expert: Subclasses must ensure that clones may be positioned at
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* different points in the input from each other and from the stream they
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public Object clone() {
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DataInput clone = null;
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clone = (DataInput)super.clone();
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} catch (CloneNotSupportedException e) {}
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public Map<String,String> readStringStringMap() throws IOException {
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final Map<String,String> map = new HashMap<String,String>();
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final int count = readInt();
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for(int i=0;i<count;i++) {
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final String key = readString();
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final String val = readString();